检索结果-南通市图书馆

Achievement of Interference Alignment in General Underlay Cognitive Radio Networks: Scenario Classification and Adaptive Spectrum Sharing

在线全文

学校读者我要写书评

暂无评论

China Communications 2018年第6期15卷 98-108页

作者： mei rong Department of Electronic and Information Engineering Chang'an University

Interference alignment(IA) is suitable for cognitive radio networks(CRNs).However, in IA spectrum sharing(SS) process of general underlay CRNs, transmit power of cognitive radio transmitters usually should be reduced to satisfy interference constraint of primary user(PU), which may lead to low signalto-noise-ratio at cognitive radio receivers(CRRs). Consequently, sum rate of cognitive users(CUs) may fall short of the theoretical maximum through IA. To solve this problem,we propose an adaptive IA SS method for general distributed multi-user multi-antenna CRNs. The relationship between interference and noise power at each CRR is analyzed according to channel state information, interference requirement of PU, and power budget of CUs. Based on the analysis, scenarios of the CRN are classified into 4 cases, and corresponding IA SS algorithms are properly designed. Transmit power adjustment, CU access control and adjusted spatial projection are used to realize IA among CUs. Compared with existing methods, the proposed method is more general because of breaking the restriction that CUs can only transmit on the idle sub-channels. Moreover, in comparison to other five IA SS methods applicable in general CRN, the proposed method leads to improved achievable sum rate of CUs while guarantees transmission of PU.

关键词： cognitive radio networks spectrum sharing interference alignment scenario classification

Continuity in Weak Topology: First Order Linear Systems of ODE

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2010年第7期26卷 1287-1298页

作者： Gang MENG mei rong ZHANG Department of Mathematical Sciences Tsinghua University Beijing 100084 P. R. China

In this paper we study important quantities defined from solutions of first order linear systems of ordinary differential equations. It will be proved that many quantities, such as solutions, eigenvalues of one-dimensional Dirac operators, Lyapunov exponents and rotation numbers, depend on the coefficients in a very strong way. That is, they are not only continuous in coefficients with respect to the usual L^p topologies, but also with respect to the weak topologies of the Lp spaces. The continuity results of this paper are a basis to study these quantities in a quantitative way.

关键词： eigenvalue Dirac operator Lyapunov exponent rotation number continuity weak topology

Dual Waterfilling Power Allocation Algorithm in MIMO Systems

在线全文

学校读者我要写书评

暂无评论

China Communications 2009年第3期6卷 144-149页

作者： rong mei Zhu Shihua Li Feng School of Electronics and Information Engineering Xi＇an Jiaotong University Xi＇an 710049 China

Aiming at the problem of resource allocation in multiuser multi-input multi-output (MIMO)systems,a new power allocation algorithm based on dual waterfilling is *** diagonalization is adopted to cancel the inter-user interference,and then the complete diagonalization method is employed to derive the spatial sub-channels for each *** overall power of the system is divided among users based on each user’s large scale fading;then the power of each user is further allocated to its spatial sub-channels based on the small scale *** results show that compared with the existing resource allocation strategies,the proposed algorithm can provide more ergodic capacity for multi-user MIMO *** the total transmit power is 100w,it has 15%capacity advantage over the traditional waterfilling method.

关键词： waterfilling resource allocation ergodic capacity

Preparation and application of efficient TiO_2 /ACFs photocatalyst

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2006年第5期18卷 979-982页

作者： LIU Jian-hua YANG rong LI Song-mei School of Materials Science and Engineering Beihang University Beijing 100083 China

Activated carbon fibers （ACFs） supported titanium dioxide （TiO2） photocatalyst was developed by sol-gel method. The surface morphology and microstructure of the photocatalyst were characterized with scan electron microscope（SEM）, X-ray diffraction patterns and specific surface area analysis. The prepared photocatalyst is specially helpful for the removal of low molecular weight organic pollutants in wastewater. Decomposition efficiency of methylene blue solution by TiO2/ACFs catalyst reached almost 100% under 60 min reaction, while the decomposition efficiency by pure TiO2 was only 25% under 3 h reaction. The mineralization of toluene aqueous solution was measured by total organic carbon instrument, and the evolution of intermediate species was detected by gas chromatograph instrument. The results indicated that the prepared photocatalyst not only enhanced the photoactivity of TiO2, but also suppressed the emergence of intermediate species, which may be more deleterious to human. The enhancement of photocatalysis was due to increased efficiency of adsorption and desorption, which were control steps in heterogeneous photocatalysis.

关键词： titanium dioxide activated carbon fibers photocatalysis toluene methylene blue

Dynamics of a Reaction-diffusion-ODE System in a Heterogeneous Media

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2024年第2期40卷 275-301页

作者： Cong-hui ZHANG Hai-feng ZHANG mei-rong ZHANG School of Science Beijing University of Civil Engineering and ArchitectureBeijing 102616China Institute of Applied System Analysis Jiangsu UniversityZhenjiang 212013China Department of Mathematical Sciences Tsinghua UniversityBeijing 100084China

The existence and stability of stationary solutions for a reaction-diffusion-ODE system are investigated in this *** first show that there exist both continuous and discontinuous stationary *** a good understanding of the stability of discontinuous stationary solutions is gained under an appropriate *** addition,we demonstrate the influences of the diffusion coefficient on stationary *** results we obtained are based on the super-/sub-solution method and the generalized mountain pass ***,some numerical simulations are given to illustrate the theoretical results.

关键词： reaction-diffusion-ODE system discontinuous stationary solutions stability asymptotic behavior monotone solutions

Characteristic analysis of photonic crystal resonant cavity in the terahertz region

在线全文

学校读者我要写书评

暂无评论

Optoelectronics Letters 2008年第2期4卷 99-102页

作者： ZHOU rong-mei CHEN He-ming College of Optoelectronic Engineering Nanjing University of Posts and Telecommunications Nanjing 210003 China

In this letter, a kind of two-dimensional photonic crystal structure applicable to THz devices is designed, and how to form a microcavity in this structure is discussed. The primary properties of the resonant cavity are analyzed, in which plane wave expansion method is used to make the calculation and the simulation. We've studied the variation of the bandgap structure and resonant frequency in THz region by changing the parameters, such as lattice constant, dielectric constant contrast and filling factor. The research results provided theoretical support for manufacturing the THz devices and the application of THz system.

关键词：特征分析光子晶体空泡光学

Three macrophage subsets are identified in the uterus during early human pregnancy

在线全文

学校读者我要写书评

暂无评论

Cellular & Molecular Immunology 2018年第12期15卷 1027-1037页

作者： Xiangxiang Jiang mei-rong Du Min Li Hongmei Wang State Key Laboratory of Stem Cell and Reproductive Biology Institute of ZoologyChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Laboratory for Reproductive Immunology Hospital of Obstetrics and GynecologyFudan University Shanghai Medical CollegeShanghai 200011China Department of Obstetrics and Gynecology Navy General Hospital of the Chinese PLABeijing 100048China

Macrophages are crucial for a successful pregnancy, and malfunctions of decidual macrophages correlate with adverse pregnancyoutcomes, such as spontaneous abortion and preeclampsia. Previously, decidual macrophages were often thought to be a singlepopulation. In the present study, we identified three decidual macrophage subsets, CCR2−CD11cLO (CD11clow, ~80%), CCR2−CD11cHI (CD11chigh, ~5%), and CCR2+CD11cHI (CD11chigh, 10–15%), during the first trimester of human pregnancy by flowcytometry analysis. CCR2−CD11cLO macrophages are widely distributed in the decidua, while CCR2−CD11cHI and CCR2+CD11cHImacrophages are primarily detected close to extravillous trophoblast cells according to immunofluorescence staining. According toRNA sequencing bioinformatics analysis and in vitro functional studies, these three subsets of macrophages have differentphagocytic capacities. CCR2+CD11cHI macrophages have pro-inflammatory characteristics, while the CCR2−CD11cHI population issuggested to be anti-oxidative and anti-inflammatory due to its high expression of critical heme metabolism-related genes,suggesting that these two subsets of macrophages maintain an inflammatory balance at the leading edge of trophoblast invasionto facilitate the clearance of pathogen infection as well as maintain the homeostasis of the maternal-fetal interface. The presentstudy physiologically identifies three decidual macrophage subsets. Further clarification of the functions of these subsets willimprove our understanding of maternal-fetal crosstalk in the maintenance of a healthy pregnancy.

关键词： CCR2 CD11c decidual macrophage subsets extravillous trophoblast cells inflammatory balance

Nutrient Release from Weathering of Purplish Rocks in the Sichuan Basin,China

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Pedosphere 2008年第2期18卷 257-264页

作者： ZHU Bo WANG Tao YOU Xiang GAO mei-rong Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu 610041 （China）

Purplish soils having high fertility with mineral nutrients inherited from the parent rock are widely distributed in the hills along the Yangtze River,especially in the Sichuan *** and field weathering experiments were conducted to mimic rock weathering and nutrient release processes in order to better understand soil fertility and nutrient compensation. Three types of purplish rock formations formed in the Jurassic period,Shaximiao(J_2s),Suining(J_3s),and Penglaizhen (J_3p),as well as one type formed in the Cretaceous period,the Chengqiangyan group(K_1c),were used in this study. Results showed that the soil formation rate was in the range from 11.2 to 19.6 mm every year,and rock weathering was in the order of J_3s>J_3p>J_2s>K_*** more rock surface was exposed to sunlight and rainfall in field conditions,pot weathering was slower than field *** release rates increased with rock weathering and was in the order similar to that of rock weathering:J_3p>J_3s>J_2s>K_*** release was the most important in all rocks;after 2 years of weathering,19.4% to 46.9% of K was released from the initial parent rocks,which suggested that K release from weathering could meet most of the crop K requirement in purplish ***,rapid release of nutrients from weathering of purplish rocks was key to nutrient replenishment and fertility of purplish soils.

关键词： nutrient release purplish rock soil formation weathering

NULL-SPACE PROJECTION AND WATERFILLING RESOURCE ALLOCATION IN MULTI-ANTENNA COGNITIVE RADIO NETWORKS

在线全文

学校读者我要写书评

暂无评论

Journal of Electronics(China) 2010年第5期27卷 701-707页

作者： rong mei Zhu Shihua Department of Information and Communication Engineering Xi＇an Jiaotong University Xi＇an 710049China

Cognitive Radio(CR) is a promising technique for the next generation mobile communi-cation system for its capability to solve the conflicts between the scarcity and underutilization of *** this paper,aiming at maximizing the system capacity of a multi-antenna CR system on the premise that avoid interference to the primary system in the same band simultaneously,a resource allocation method which is able to avoid interference between PRimary(PR) and CR users by pro-jecting the transmit signals of CR users on the null space of the PR users' channels is *** users with better channel condition are selected,and the interference from CR system to PR users can be removed completely by projecting the transmit signals of CR system on the null-space of PR users' *** sub-channels are constructed for CR users through Singular Value Decomposition(SVD).At last,waterfilling is also adopted to increase the CR users' *** result demonstrates that compared with existing methods,our method can improve the achievable sum rate of CR users as well as reduce the outage probability of PR users.

关键词： Cognitive Radio (CR) network Resource allocation Null-space projection Waterfilling